Inductor leveling switch



y 1952 J. H. BORDEN 2,598,214

INDUCTOR LEVELING SWITCH Filed July 5, 1949 5 Shests-Sheei; l

INVENTOR.

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INDUCTOR LEVELING SWITCH Filed July 5', 1949 I 5 Sheets-Sheet 2 IN V EN TOR.

1% m Joseph H 50/??? May 27, 1952 J. H. BORDEN 2,598,214

INDUCTOR LEVELING SWITCH Filed July 5, 1949 5 Sheats-Sheei I5 INVENTOR. L/O $/O/I Border? May 27, 1952 Y J. H. BORDEN 2,593,214

INDUCTOR LEVELING SWITCH Filed July 5, 19 49 5 Sheets-Sheet 4 INVENTOR.

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INDUCTOR LEVELING SWITCH Filed July 5, 1949 5 Sheets-Sheets IN V EN TOR.

- dosed; h! 50rd? w ww T RNEVS Patented May 27, 1952 INDUCTOR LEVELING SWITCH Joseph H. Borden, Toledo, Ohio, assignor to Haughton Elevator Company, Toledo, Ohio, a

corporation of Ohio Application July 5, 1949, Serial No. 102,967

19 Claims. 1

This invention relates to inductor switches and in particular to inductor switches that are operated by cooperation with a relatively movable magnetizable plate and that are arranged so that particularly at one end of the plate the switch is extremely sensitive to relative movement between the switch and the plate along a path parallel to the plane of the plate and insensitive to variations in spacing between the switch and the plate in a direction perpendicular to the plate.

Inductor switches have been proposed from time to time for use in controlling electrical circuits according to the position of a movable member such as an elevator car. These previously known inductor switches are suitable only for coarse indication of position because the position at which the switch contacts close as the member approaches a predetermined position differs materially from the position at which the contacts open as the member recedes from the fixed position. There is thus an. appreciable zone of movement within which the contacts remain closed if closed and open if open. In this respect these inductor switches perform much the same as a toggle operated switch that depends upon the overcenteraction of a spring to rapidly move the contacts from open to closed position or vice versa. Another difficulty encountered with most if not all inductor switches is that if the switch is arranged to cooperate with a plate of appreciable length the relative position at the end of the plate at which the switch operates varies with the transverse spacing between the switch and the plate.

The principal object of this invention is to provide an inductor switch that is suitable for cooperation with a magnetizable plate of considerable length in the direction of relativemovement between the switch and the plate", which switch is arranged to be, particularly at one end of the plate, extremely sensitive to relative movement along the length of the plate and insensitive to movement perpendicular to the" plate.

Another object of the invention is to provide an inductor switch that cooperates with a magnetizable plate and that opens and closes its contacts at substantially the same relative position between the switch and the plate whether the switch is approaching or receding from the plate:

A still further'obje'ct of the invention is to provide an inductor switchw suitable for operation with-a. magnetizable plate of appreciable length and: capable of? operating without. appreciable uncertainty at a. definite relative position. between 2 the plateand switch regardless of appreciable variation in spacing perpendicular to the path of relative movement.

More specific objects and advantages are apparent from the following description of several forms of improved inductor switches constructed according to the invention.

According to the invention the range of uncertainty observed in ordinary inductor switches is eliminated by arranging pivotally mounted magnetic pole pieces to extend like com ass needles along the direction of the lines of force of the magnetic field and to be operated by changes in direction of the field. The position along the intended path of relative movement of the switch and plate at which the contacts operate is made substantially independent of transverse spacing between the switch and the plate by arranging the magnetic field to extend obliquely to such path from the magnet toward the approaching edge of the magnetizable plate. In this arrangement the pivoted pole pieces of the magnet are carried at the poles of the magnet to extend along and serve to concentrate the magnetic flux that follows a closed path from one pole of the magnet through the pivoted pole piece carried on that pole, across the gap to the side and edge of the magnetizable plate, through the plate and out the same side of the plate and across the gap to the other of the pivoted pole pieces and thence to the other pole of the magnet. Since the magnetizable plate is long in comparison to the space covered by the magnetic field the magnetic flux threading the pole pieces and extending across the gap spreads over a marginal area of the approaching plate that varies according to the spacing between the pole piece and the plate. By selecting the angle at which the magnet and pivoted pole pieces are placed with respect to the path of relative movement of the switch and plate the tendency of the field to spread and include a marginal. area of the plate that varies with the spacing. is utilized to maintain a fixed operating point along the path of movement regardless of variations: in lateral spacing.

The improved switch may be advantageously employed as a leveling switch for passenger and freight elevators. In this use a plurality of switches preferably are mounted on the elevator car while magnetiza'bl'e plates, one for each floor to be served by the car,- are mounted in the elevator shaft preferably from the track that guides the car. The mounting arrangement may be reversed with tl'i'e plate on: the carend the switches in the shaft. In the operation of a high speed elevator a number of controls are automatically called into action in stopping the elevator car and leveling it with respect to the floor being served. The sequence of control operations as the car approaches a floor includes first switching the car from the high speed running condition to a deceleration condition when the car is approximately 10 to 12 feet away from the floor being served. The deceleration characteristics are adjusted so that the car will be moving at fast approach speed when it is approximately 2 feet away from the floor. At this point one of the inductor switches mounted on the car comes opposite the magnetizable plate to establish the controls in the fast approach speed. This condition holds until the car is approximately 6 to 10 inches (the exact distance being varied by adjustment to suit the particular elevator) away from the floor when another inductor switch is operated by cooperation with the plate to call for slow approach speed. The car then decelerates until it is moving slowly so that it is ready to stop the instant the magnetizable plate leaves the first closed inductor switch thus permitting that switch to open. Should the car overrun, another inductor switch (normally operated if the car is approaching from the other direction) is energized to establish a reverse slow speed approach condition thus bringing the car back to the selected floor. A small dead zone is permitted between the opening of the first energized inductor switch and the closing of the reverse direction switch so that the car may come to a stop rather than be continuously moved first above and then below the selected floor. The successful operation of such a control depends upon the accuracy of operation of the inductor switches, particularly those that act to stop the car at the end of the slow speed approach. Previously known inductor switches :because of their overcenter effecthave an uncertainty zone which adds to and thus objectionably extends the required dead zone with the result that it-is practically impossible to maintain close leveling of the car with respect to the building floor. improved inductor switches constructed according to the invention permit much more precise leveling than previously obtainable because they have no appreciable uncertainty zones to extend the dead zone and further because the position at which they respond to the magnetizable plate is,

for over an appreciable distance, unaffected by horizontal movement of the car resulting from looseness or play between the rollers or shoes of the car and the guide rails.

Several examples of the improved inductor switches are illustrated in the accompanying drawings.

In the drawings:

Figure I is a simplified schematic illustration of an elevator car and fragments of the guide rails as well as structural members for supporting the magnetizable plate that cooperates with the inductor switch mounted on the car.

Figure II is a schematic illustration of one form of inductor switch constructed according to the invention.

Figure III is the same as Figure II except that it shows the effect of displacing the magnetizable plate laterally with respect to the inductor switch.

Figure IV is a diagrammatic illustration to 10W the principle of operation of another embodiment of the improved switch.

Figure V- is the same as Figure IV showing the The effect of increasing the lateral spacing between the switch and plate.

Figure VI is a plan view of the structure of a switch constructed according to the switch illustrated in Figures II and III.

Figure VII is a side elevation of the switch shown in Figure VI.

Figure VIII is an end elevation of the switch as seen from the line VIII-VIII of Figure VI.

Figure IX is an end elevation of a modified form of switch embodying the invention.

Figure X is a plan view of the switch shown in Figure IX.

Figure XI is a sectional view, as seen from the line XI-XI of Figure X, showing the magnetic structure of the switch shown in Figures IX and X.

Figure XII is a detailed view as seen from the lin XIIXII of Figure IX.

Figure XIII is a perspective view of a switch constructed according to the invention and schematically illustrated in Figures IV and V.

Figure XIV is an elevation with the case being shown in section of the switch illustrated in Figure XIII.

Figure XV is a section taken substantially along the line XVXV of Figure XVI.

Figure XVI is a section taken along the broken line XVI-XVI of Figure XV.

These specific figures and the accompanying description are intended merely to illustrate the invention but not to limit its scope.

In an ordinary elevator construction a car I is supported by a plurality of cables 2 that are carried over sheaves of a driving motor at the top of the elevator shaft. The car is fitted with guide shoes 3 that run on tracks 4 secured to the walls of the elevator shaft. A control cable 5 depending from the bottom of the car carries the electrical conductors for the car controls such as floor selector buttons, floor indicating lights, leveling switch circuits, lights and other miscellaneous electrical connections. The tracks 4 are usually T-shaped in cross section with the guide shoes 3 running on the flange constituting the stem of the T-shape. A magnetizable plate 6 is mounted adjacent the path of the elevator car I and is supported on brackets 1 clamped to a frame member 8 and engaging an up-turned edge of the plate 6. The frame member 8 is shown as a separate member in the drawings whereas in actual construction it is customary to mount the magnetizable plates 6 from one of the tracks 4. A plurality of inductor switches l0, ll, 12 and I3 are mounted on the elevator car I in position to cooperate with the magnetizable plate 6.

As shown in the drawing the plate 6 has its ends rounded in the manner of a sled runner. This is to prevent catching and damage should the cases of the switches H] or l3 strike the end of the plate.

The inductor switches Ill, H, l2 and I3, preferably of the type illustrated in detail in Figures XIII to XVI inclusive, are arranged in the control circuits for the car in substantially the same manner as were the mechanically cam operated switches previously used for elevator car control. The circuit and operation of these switches is such that if the car is approaching a floor from below, the switch I0 is first closed as it comes opposite the lower end of the magnetizable plate 6. The closing of this switch conditions the control for fast approach speed. As the car continues at fast approach speed, the inductor switch ll closes as soon as it comes opposite thelower end of the plate 6 but this closin hasv no efiect upon the control because ordinarily the switches II and I2 are connected in series. Amoment later, when the car is about 6 inches from the desired stopping point, the switch l2 comes opposite the lower end of the plate and closes thereby completing the circuit conditioning the control for slow approach speed. This condition holds until the inductor switch l0 passes beyond the upper end of the plate 6 at which point this switch opens. Theopening of the inductor switch l0 causes circuits to operate to immediately stop the car. Should the car overrun slightly the inductor switch !3, the bottom one on the series, is operated and it in conjunction with the now closed switches II and 12 conditions the car for slow speed approach in the downward direction to bring the car back to its proper stopping point. The dead zone, in which no circuits operate to cause the car to move, thus extends between a lower position at which the inductor switch (0 just closes and an upper position at which the inductor switch [3 just. closes. The inductor switches Ii to l3 inclusive are adjustably mounted on the car so that I a service man may easily adjust their positions relative to the magnetizable plate 6.

If it is desired to extend the slow speed approach zone the inductor switches H and I2 are moved closer together. the zone still further after the switches are brought practically into contact with each other they may be connected in parallel so that the first switch to operate then conditions the circuits for slow speed approach. This reverses the effect of the spacing of the switches so that still further lengthening of slow speed zone may be accomplished by moving the switches, It and 12 further apart until finally they are brought adjacent the outside switches l0 and I3. is done a slow speed approach zone approximately equal in length to the length of the magnetizable plate '6 is provided. Normal operation. however, requires that the switches be connected in series since slow speed approach. zones of 6 to 8 inches in length accommodate most elevator applications.

Inductor switches constructed according to the invention may take many forms. They may be arranged to operate entirely from one side of the magnetizable plate such as the inductor switches IG, H, [2 and I3. They may also be arranged in interconnected pairs with the magnetizable plate passing between the pivoted pole pieces of each pair. This latter construction is illustrated schematically in Figures II and III and switches constructed according thereto are shown in detail in Figures VI to XII inclusive. Referring particularly to Figures II and III, which are the same except for the position of a magnetizable plate or vane M with which the switches cooperate, the switches each comprise a pair of pole pieces 55 that are pivotally mounted from frame members It and II. The pole pieces l5 are interconnected by a link l8: ar-

the pole. pieces 155 have the same polarity and thus in the absence of the. plate. [4 hand to. repel each other; thereby opening the contacts and If it is desired to. extend If this holding themv in open condition. As the plate I4 enters the region between the pole pieces the lines of. force of the magnetic field. bridge the gap between the tips of the pole pieces t5 and the adjacent marginal areas ofv the plate M. The magnetic lines. of force or flux lines spread over a marginal area, of the plate that varies according to the distance to the plate and the orientation of the plate the field. In the. position indicated. .in. Figure II, the position. at which the contacts are just ready to close upon continued downward movement of the plate [4, the resultant magnetic pull of the magnetic field extends along a. line through the pivoting axis of pole pieces 15' the pole tips of the pole pieces and. intersects the side of the plate It at a small. distance from the lower edge thereof. As the plate moves downward the flux. continues .to concentrate in the marginal area of the plate and. the pole. pieces [5, like compass needles, continue to point toward that area and thus'rotote onv their pivots as they follow the movement of the plate. Regardless of which direction. the plate moves the pole pieces immediately follow because they are. positioned. by the direction of themagnetic field rather than by changes in the intensity of such field. As long as. the plate I4 is equally distantfrom the pole pieces #5 the flux entering its sides is equally distributed.

In the event that the plate is displaced laterally from its mid-position the operating point of the contacts 19 and Z0 is not materially changed. This condition is illustrated in. Figure III and the reason that the operating point is not afi'ected is because the marginal area on one side of the plate It covered; by the magnetic flux shrinks as the. plate approaches one of the pole pieces and the covered area on the other side enlarges: as. the plate leaves the other pole pieces. Since the position of the pivoted pole pieces i5 depends upon the resultant. of all the lines of force the pole pieces are aligned with the resultants. of the flux: fields regardless of where the: resultant flux intersects the plate. Thus as the plate is; displaced toward the left in Figure III, the marginal area covered by the flux on the left side oi the plate decreases and the effective. center of the field is nearer the bottom edge of the plate. Likewiseon the right hand. side the flux. spreads. over .a larger area and its center moves upward. away from. the edge of the plate.

By proper selection of. the angle of the pole pieces relative to the path of movement oi the plate and the spacing between the pole pieces and the plate it is possible to. find an operating point at which the change in marginal area covered by the flux varies. at such arate that the resultant force at the pivoted. poles is independent of horizontal position of the plate. This particular construction, because of the duplication of magnets and pole pieces on each side of the plate, has a rather wide tolerance on the lateral position of the plate.

Substantially similar results. may be obtained by a single magnet inductor switch such as is schematically illustrated in. Figures IV and V. In this construction, which is: typical of the in ductor switches 10V to. Hi inclusive, apole piece 21 is pivotally mounted on the end of a magnet pole; 22. The magnetic flux. from the magnet after threading through the pole piece 21 establishes a field that. cooperates with a plate :23 for producing limited rotary movement-of the pole pieces 2| to operate contacts 24 connected thereto.

In this arrangement the pole piece 2| acts as and the plate 23 asmeasured in a direction perpendicular to the plate. Since the pivoted pole piece 2| tends to align itself with the field it points toward the magnetic center of the marginal area on the side of the plate 23. Since this magnetic center varies in position from the edge of the plate, moving up on the plate as the plate moves laterally away from the pole piece,

it is possible to select an angular orientation for the magnet and pivoted pole piece 2| with respect to the path of relative movement of the plate so that the magnetic field at the tip of the pole piece 2| does not vary in direction with lateral movement of the plate. This is illustrated in Figures IV and V which are identical except for the spacing between the tip of the pole piece 2| and the plate 23. Thus when these members are relatively close together the magnetic flux entering the plate 23 is concentrated in the side of the plate near the lower edge thereof so that the pole piece tries to point directly toward the 1 center of this area. As the plate is moved back as indicated in Figure V the flux entering the side of the plate spreads over a larger marginal area with the resultant center of the flux located substantially further from the edge of the plate. The operating position of the pole piece 2| and contacts 24 may therefore be selected so that without movement of the pole piece the pole piece continues to point toward the center of the marginal area of plate covered by the magnetic flux as the vane is moved laterally with respect to the pole piece. In general the pivoted poles and magnetic field to secure this independence of contact operation with lateral movement of the vane should be oriented apv proximately 45 from the path of relative movement between the inductor switch and plate.

However, depending upon the actual configuration of the pole tips and the end of the plate it may be desirable to increase the angle so that the pole pieces are more nearly perpendicular to the plate in their contact operating position. In this connection it might be mentioned that the provision of sled runner ends on the vane as indicated in connection with Figure I may make it desirable to modify the shape of the ends of the pivoted pole pieces to provide satisfactory operation.

In each form of switch constructed according to the invention the pivoted pole pieces are counterbalanced so that they are in substantially neutral equilibrium and are thus not affected by acceleration or vibration of the elevator car on which they may be mounted. In each form of construction the pivoted pole pieces in at least one operating position are aligned with the magnetic flux so as to operate as compass needles in aligning themselves with the magnetic flux rather than as solenoid armatures that move. in the di -rection of the field to shorten the magnetic path.

It is this shortening of the magnetic path wih movement of the armature of a solenoid or relay that introduces the uncertainty of positioning making inductor switches so operated unsuitable as precision leveling switches.

This feature of operating the pole pieces in the manner of compass needles and orienting the pole pieces so that in operating position they. are directed obliquely toward the magnetizable plate makes the operating position of the pole pieces practically independent of the strength of the magnetic field so long as the magnet strength is sufficient to overcome the frictional resistance of the mounting for the pole pieces. The change in magnet strength may result from changes in the magnet structure itself or from variations in the spacing between the pole pieces and the path of the magnetizable plate.

An inductor leveling switch suitable for use with an elevator car and constructed according to the principles illustrated in Figures II and III is shown in Figures VI, VII and VIII. This switch comprises a frame 25 mounted on the elevator car or other body the position of which isto be indicated. A pair of frame arms 26 extend from the frame 25 transversely to the path of movement of the body. In an elevator car for example the arms 26 are positioned horizontally. Permanent magnets 2': are rigidly clamped as by means of clamps 28 to the frame arms 26 and extend parallel to these arms. Each of the magnets 21 serves to magnetically energize a generally 0- shaped frame comprising pole pieces 29 and 30 rigidly interconnected by a non-magnetic bar 3| and carrying magnetizable pole extensions 32. These -Cshaped frame assemblies are pivotally supported on cone-pointed screws 33 that engage the pole pieces substantially in line with the ends of the magnets 21. The magnets 21 are oriented so that adjacent ones of the pole piece extensions 32 have like polarities and thus tend to repel each other.

Referring to Figure VIII each pair of C-shaped pole piece assemblies are interconnected by a linkage 35 so that the assemblies move in opposite directions and in generally equal amounts during the passage of the magnetiaable plate 34 therebetween. When the plate 34 occupies the position shown in Figure VIII the upper pair of pivoted pole piece assemblies rotates to a position tending to separate the contacts of an electrical switch 36 operatively connected to the linkage 35. In the position shown the magnetic flux from the magnets 27 threading across the air gap from the pole pieces to the plate 34 induces magnetic poles in the magnetizable plate 34 of opposite polarity so that attractive forces are set up tending to pull the pivoted pole extensions 32 toward the adjacent edge of the plate 34. When the plate is in the position shown these attractive forces urge the upper right hand pole piece in a counterclockwise direction and the upper left hand pole piece in a clockwise direction thus tending to move the linkage 35 toward the right to separate the contacts. As the magnetizable plate 34 moves upwardly relative to the upper set of magnets and pole piece assemblies (which also occurs upon downward movement of the inductor switch assembly) the pole extensions 32 continue to point toward the nearer edge, the upper edge, of the plate 34 rotating on their pivots in following the movement of the plate and thereby moving the linkage 35 to the left to close the contacts.

The contacts remain closed as long as the plate 34 is between the pole piece extensions 3?.. As

arose the plate moves still further and passes beyond the-extensions a point is finally reached at which the repulsive forces between the'pole piece extens'ions 32 overcome the attractive forces and the pole pieces then rotate to separate the contacts. Action at this second position may be referred to as operation of the contacts in the non-sensitive cooperative position between the switch Landzplate because in this cooperative relation the pole pieces do not'point toward the area of the plate linked by ithemagneticflux. .In this latter condition the flux is generally along the :path @of movement of the pole piece extensions and they operate as ordinary relay armatures.

The .lower pair of magnets and inductor "switch pole piec'e'assemblies 2.9a aresimilar in arrangement and operation to thosejust described except that "the magnets are oppositely polarized. -This opposite polarization is preferable although not necessary. TBy oppositely polarizing the lowerset of magnets :in :relation to the upper set as seen in :Figure VIII :the .pole .piece extensions 32a "of theiowerrset .are repelled :from each .011161 while they .are attracted toward the pole piece extensions of thetupperiswitch assemblies thus insuring that the electrical switches remain open whenever therma'gnetizableplate 34is absent.

This :switch is practically immune :to .small lateral imisalignment of the .magnetizable plate 34 because of two effects. that the flux linking with the .plate'tends to spread over aimarg'inaljtareathat varies Withithe lateral displacement 'of the plate :so that the pole pieces in operative position point toward the center '"of "such marginal :area. The second effect is produced by the linkage 35 which :equalizes the movement of the pole :pieces.

'Another embodibent of the invention is ii'llustratedin Figures IXcandXII :inclusive. this embodiment standards :3"! erected from an :elevator car "or other member "support a ".U-shaped housing 38. The inductor switch mechanism is mounted within the U-shaped housing while a magnetizable plate or vane 391is arrangedto pass through the opening of the housing :aaas it-cooperates with the :switch. The .switch 1316111811118 themselves comprlse vpermanent magn-et :bars i410 that are clamped :to a'brack'et 4i mountediwithinthe housing 38. Poles-pieces '(see also Figure XII) are pivotally mounted'on thesides of the magnets '40 one 1168.1"163'611 end of each of the magnets. The pivoted pole pieces 42 on each magnet areconnected-by fa c-shaped frame 413 that *also :carriesxa balance weight 44 soithat :the pivoted pole pieces are .in substantially r-neutral equilibrium "and thus :able to're'adily respond "to any magnetic forces tending to rotate them around their :pivoting axes. .TIn 'a-ddition, the shaped frames-43 are'each provided with a laterally: directed lug-45 to which a link fli is pivotally connected. The link "46 serves to equalize the movementofthe pivoted pole pieces as well'as' to carryone contact of an electrical switch 18. As is :clearly indicated in the drawings, the pivoted po'le pieces '12 extend obliquely toward thepa'th of relative movement' between the plate 39land the inductor switch. As theplate 3'9 moves into the "space between the ends :of the pivoted pole pieces 42 the pole pieces move toward'each other thus closing the switch-48 opera'tivly connected :to the pole pieces 42 through 'the :link' fli. Furthermore the magnets' are oriented with like .pole's "adjacent. each other ..so that in the :absence of the'lplate :39 the pivote'd pole gpieces fl repelieah :othertoopen the'switch-contacts.

The firstrof these is This switch, like the one-previously described, provides high sensitivity to relative movement of the plate 3.9 when the plate is approximately in the position shown. This high sensitivity with freedom from uncertainty in operating position results because the contact operation is produced by :a compasssneedle like :action of the pole pieces as they point toward the :lower marginal areas of the sides .of the :plate 39. In this arrangement therexis'no changein length of the magnetic path produced solely by movement of the pivotedv'pole pieces. .Thus .the operating position of the switch is the same whether the 'magnetizable plate be moving-toward or away from the pole pieces :at the position-shown in Figures TX to XIinclusive. As longasthe plate.3.9 isbelow the position shown the contacts 'will obviously fbezclosed while if it is at or ::above the position shown the contacts are :open.

In this example as in the preceding example lateral displacements of the 'magnetizable plate 39 do not materially alter the position along the path of relative movement at which the contacts are operated. This result follows because of the link 46 connecting the pole ;pieces as well as .becauseof the fact that thegpole pieces point toward an effective center of each marginal area'of the plate that varies in height on the plate according to the lateral displacement of the plate. Again by proper selectionof the angular position of the pole pieces to which the contacts are operated it is, possible to make the switch practicallyimmuneto lateralmisalignment.

Switches constructed according to this second example are-used in pairs to cooperate, in their sensitive positions, one with the upper edge of themagnetizable plate and the other with the lower edge. Thus .two of these :switches are required "to perform the same function 2&5 that performed by the complete switch shown in the preceding example.

In the two examples just described magnets and pole pieces are arranged-onboth sides of the cooperating magnetizable plate. While this arrangement provides some advantage because of the compensation resulting from increasing the spacing of the plate from one set of pole pieces while the; spacing from the other setrisdecreased, satisfactory operation of an inductor switch may be obtained with ,a structure that is essentially one-half of the arrangement shown in this sec-- ond embodiment (Figures IX to .XH). Such .a switch with some modifications is illustrated in Figures XHI to XVI inclusive.

This construction, which is preferred because of its :simplicity both in construction of the switch .itself :and in its .mounting foruse, comprises a generally cubical case 50 constructed'of brass :or .:other non-magnetic material. One side of the case has aninsulating strip fil through which terminalfleads are taken and another side of the case has sawindow 52 through which the operation of the contactsmay -be observed. The mechanism of the switch itself is "mounted from a stainless steel or *other hard non-magnetic plate-53 which serves as'a cover for'anotherside of the cubical case 50. This switch-isdesigned to cooperate with a' magnetizable 'plate 54' a'fra'gmentof which is shown in Figure-XIV. The end of the *p1ate'5'4 may be eitherstraight or bent .as shownto provide a sled runner efiectso that the plate cannot catch on the-corners of'the case if an excessive amount of misalignmentshouldnocour.

"The 1 operating mechanism of the switch itself.

contained within the cubical housing 50, is mounted from a bracket 55 which for convenience in assembly is attached to the cover plate 53. The mechanism comprises a U-shaped permanent magnet 56 that is arranged at an angle to the path of relative movement between the switch and the magnetizable plate 54. On the pole faces of the magnet '56, which are directed toward the nearer end of the plate 54 when the plate is in sensitive contact Operating position as shown in Figure XIV, are pivotally mounted a pair of pole pieces 51 that are furthermore rigidly interconnected by a generally T-shaped non-magnetic plate 58. The pole pieces .51 are mounted near the ends of the cross bar of the T-shape.

The' magnet 56 and the contact mechanism of the switch are mounted from a non-magnetic support plate 59 the magnet being clamped thereto by a pair of bolts 60 that extend through a fiber block 6|, through the bight of the magnet 56, through the mounting plate 59 and through the bracket 55. The fiber block 61 which may be of Bakelite or other insulating material serves as a base for the stationary portions of the switch mechanism. The moving part of the switch is carried on the T-shaped plate 58 and more particularly from the stem of such plate.

The stationary parts of the electrical contacts of the switch include a generally Z-shaped arm 62 that is secured at one end of the fiber block Bl by means of a bolt 63 that also serves as an electrical connection to an incoming lead 64 which in turn is connected to an external terminal 65 (see Figure XIV). The free end of the Z-shaped bracket carries an adjustably mounted contact 66 that cooperates with contacts carried on a leaf 6'! constituting the moving arm of the switch. A second stationary contact 68 is adjustably mounted from a small metallic plate '69 which in turn is secured to the fiber block 6| by an attaching bolt serving as a connection for a lead H the other end of which is attached to an external terminal 12 of the complete switch assembly.

The movable switch plate 61 is secured to a fiber block 13 mounted on the side of the stem of the T-shaped plat 58 carrying the pivoted pole pieces 51. A flexible pig-tail lead I4 is connected between the mounting bolt 10 holding the second stationary contact and a screw that serves to secure the moving switch leaf 6'! to the fiber block 13. Thus the second stationary contact is always electrically connected to the moving switch arm and therefore serves merely as an adjustable stop to limit the travel of the switch arm in a direction away from the first fixed contact 66 which is mounted on the end of the Z-shaped arm 62.

A piece of thin spring wire 16 one end of which is held under one of a number of screws 11 attaching the pivoted pole pieces 51 to the T-shaped plate 58 has its other end loosely fitted through a transverse hole in a stud l8 adjustably mounted in the fiber block 61. The forces exerted by this spring 16 are verw small in comparison with the magnetic forces involved when the inductor switch cooperates with the magnetizable plate 54. The function of the spring 16 is to provide a small force tending to move the pivoted pole pieces and T-plate assembly to separate the movable contact leaf 6! from the first fixed contact 66 so that the switch is open when it is not under the influence of a magnetizable plate.

Furthermore, so that acceleration forces, which may be applied to the switch because of the movement or vibration of the member upon which the switch is carried, shall not cause false operation of the switch the T-shaped plate 58 is provided with a balance weight 19 of such size and location that the assembly of pole pieces and T-shaped plate is in neutral equilibrium with respect to the pivoting axis of the assembly. This pivoting axis is defined by chisel-shaped edges provided on the edges of the pivoted pole pieces 51 where they rest on the pole faces of the magnet 56.

To prevent derangement of the pole pieces with respect to the magnet a pair of non-magnetic U-shaped metallic strips BI and 82 are attached to the non-magnetic mounting plate 59 r with the up-turned ends of the U-shaped plate 8| serving as thrust plates cooperating with the corners of the pole pieces 5'! at the inner ends of the chisel-shaped edges 80 to prevent movementof the pole pieces parallel to the pivoting axis. The other U-shaped strip 82 is provided with V-shaped notches the sides of which engage the chisel edges 80 of the pole pieces 51 to keep the pole pieces centered on the pole faces of the magnet.

In the construction of the pivoted pole pieces 51 the edges are beveled symmetrically from each side to form the chisel-pointed pivoting edges 80 so that the magnetic forces acting between the pole pieces and the pole faces are substantially symmetrical about the pivoting axis and thus do not bias the pole pieces in either direction.

If it were not for the precision required in manufacture it would be practical to disturb the symmetry of the chisel-shaped edges and locate the sharp edge off center so that the magnetic forces supply the small restoring force normally provided by the spring 16. In actual construction however the spring is preferable because not only is it easier to make but it may also be adjusted to compensate for inaccuracies in the formation of the chisel-shaped edges 80 and thus secure the proper biasing force for satisfactory operation.

It will be noted that the free ends of the pivoted pole pieces 51 are bent upwardly as seen in Figure XIV so as to extend for a short distance parallel to the path of relative movement between the inductor switch assembly and the magnetizable plate 54. This arrangement was selected to provide more positive operation of the switch and to compensate for the sled runner ends of the magnetizable plate 54.

These inductor switches are normally employed in the arrangement illustrated in Figure I there being four of the switches mounted on each elevator car with two of the switches serving as final leveling position controls and the other two serving to control the changeover from fast approach speed to slow approach speed. Identical switches are used in all four positions even though the superior operating characteristics of the improved switch are required only in the two switches determining the final leveling position. The improved switch as illustrated in Figure XIII to XVI inclusive is simple enough in construction that it is more economical to standardize on this particular switch than to carry two types of switches, one for final leveling and the other for approach control.

In reference to Figures I and XIV it will be noted that the relative position of the inductor switch assembly and the magnetizable plate 54 as shown in Figure XIV is reached when the elevator car is level with the floor. In arriving at this position one of the switches has just 13 passed through its zone of cooperation with the magnetizable plate while the other "of the cooperating switches has, just failed to reach its zone of cooperation. The operation of the switch may be understood by considering that the switch assembly illustrated in Figure XIV is mounted in a position corresponding to the switch I3 :01? Figure I. Assuming that the car is approaching the desired floor from a higher floor, the first cooperation between the pivoted pole pieces 5! and the magnetizable plate '54 occurs when the upper end of the plate 54 (marked 54') is approximately in the position shown by the dotted line position in Figure In this position the magnetic field extending from the pole pieces to the magnetizable plate is substantially parallel to the path of movement of the ends of the pivoted pole pieces. As a result the operating .point of the switch, which is operated by counterclockwise movement of the pole pieces, varies with the lateral spacing of the magnetizable plate from the switch assembly. This is of no material disadvantage because this operatin position is not critical in the control of the elevator car. This relative position and switch operation occurs at a point about two feet from the final leveling position. This switch operation merely conditions the controls. to insure that the car is moving at fast approach speed in the zone extending between points. spaced approximately two feet and about six inches, from the final leveling position. As the car continues downwardly and the magnetizable plate 54 appears to move upwardly with respect to the switch assembly it finally reaches the relative position shown by the solid lines in Figure XIV. In this position the pivoted pole pieces 51 have rocked clockwise to open the contacts of the switch. In this cooperation the pole. pieces are very sensitive to movement of the magnetizable plate in a vertical direction as shown in the figure and have no appreciable uncertainty zone since they point, like compass needles, toward the magnetizable plate to follow. every minute movement of the plate.

In this position of cooperation the contacts. may

be positively made or broken by one thirty-second of an inch movement of the elevator car. Furthermore by careful selection of the. angular position of the magnet and pole pieces, having in, mind the. compensation required by the sled runner effect on the end of the magnetizable plate 5,4, the. tendency of the magnetic .fiux to spread over the lower marginal area. ofthemagnetizable plate is employed so that the plate may move laterally in either direction from the position shown without causing movement of the pivoted pole pieces. This condition obtains for. a, horizontal variation in spacing that is-appreciably greater than the total horizontal movement of the elevator car that may occur through slack, or looseness in the fittings oi the guide shoes or rollers connecting the car to the guide tracks.

This improved inductor switch whilerela'tively simple of construction and design is nevertheless capableof, providing a precise indication of relative. position of av pair of relatively movable members. and. of indicating that position accurately regardless of much larger movements-in transverse directions. Furthermore it has the advantage that the indicated position is independent of the direction of relative movement by which that position is approached.

Various modifications in detail of construction of inductor switches employing obliqdely-directerl pivoted pole pieces cooperating with the. marginal area of a magnetizable plate may be made without departing from the spirit and scope of the invention.

Having described the invention, I claim:

1. An inductor switch for generating signals for controlling the relative position of one member with respect to another member through an extended zone of relative movement which switchat one end of the zone is sensitive to relative movement of said members along the intended path of movement and insensitive to relative movement transverse to said intendedpa'th, comprising in combination, a magnetizab'le plate included in one of the members, said plat being parallel to the path of relative movement and generally equal in length to said zone, a magnet assembly included in the other member, said as,- sembly comprising a magnet and a pole piece pivoted at a pole of the magnet, said pole piece being directed obliquely toward said plate, and extending generally along a line from the magnet pole to the marginal area at the end of the plate.

as the magnet assembly passes beyond the sensitive end of the zone.

2. An inductor switch for energizing positioning controls, according to the presence within an extended zone of a first member with respect to a second member, which switch particularly at one end of the zone is sensitive to relative movement of the members along the length of the zone and insensitive to movement transverse to the length of the zone, comprising, in combination, a magnetizable plate included in one of the members, said plate being located along the path of relative movement of the members and generally equal .in length to the zone, a magnet assembly included in the other member, said assembly comprising magnet and a pole piece pivoted at a pole of th magnet, said pole piece being directed obliquely to the path of relative movement of the" members and. toward the marginal area of the plate as the magnet assembly passes beyond the sensitive end of the zone, said magnet assembly and magnetizable plate producing a magnetic field that spreads with increasing transverse separation of said members to cover a larger marginal area of said plate and maintain generally unchanged the oblique direction of the field about the end of thepole piece.

3. An inductor switch for signalling throughout an extended zonec'f relative movement therelative position of a first member with respect to a second member, which switch at th end of the zone. has high sensitivity to relative movement along the zone and low sensitivity to movementduringthe time that the magnet assembly is located just beyond the end of the plate.

4. An inductor switch that is actuated by cooperation with a relatively movable magnetizable plate, said switch comprising a magnet for establishipg a magnetic field, and a pole piec pivoted at a, pole of the magnet for operating electrical contacts, said switch being characterized by having the contact operating position of the pivoted pole piece oriented obliquely to the path of relative movement of the magnetizable plate and in line with the magnetic field that, when the switch is just beyond the end of the plate, links with the marginal area of the end portion of the plate.

5. An inductor switch which is actuated by -magnetic cooperation with a relatively movable magnetizable plate and which at one end of the zone of cooperative positions of the switch and plate is sensitive to relative movement lengthwise of th plate and insensitive to movement perpendicular to the plate, said switch comprising a magnet for establishing a magnetic field and a pole piece pivoted at a pole of the magnet and arranged to operate electrical contacts, said pole piece in contact operating position being oriented obliquely to the plane of the plate and the path of relative movement so as to point toward the nearer marginal area of the plate and to rotate through a small angle as the plate moves relative to the switch so as to continue to point toward such area as the plate approaches or recedes from the switch.

6. An inductor switch that is actuated by magnetic cooperation with a relatively movable magnetizable plate extending parallel to the path of relative movement of the switch and plate, said switch being characterized by having contact operating po1e pieces pivotally mounted at the poles of a magnet of the switch and extending obliquely to the path of relative movement of switch and plate in alignment with flux passing from the pole pieces to the plate.

7. An inductor switch that is actuated by magnetic cooperation with a relatively movable magnetizable plate extending parallel to the path of relativ movement of the switch and plate, said switch comprising a magnet, pole pieces pivoted for limited rotation about the pole tips of the magnet, and cooperating electrical contact elements one of which is operatively connected to the pole pieces and the other of which is fixed with respect to the magnet, said switch being characterized by having the pivoted pole pieces oriented along the lines of force of the magnetic field and obliquely to the path of relative movement of the switch and plate, whereby the pole pieces are predominantly responsive to changes of direction of the magnetic field as the switch enters and leaves the zone of cooperation with the magnetizable plate.

8. An inductor switch that is actuated by magnetic cooperation with a relatively movable magnetizable plate extending parallel to the path of relative movement of the switch and plate, said switch comprising a pair of magnets, a set of pole pieces pivotally mounted for limited rotation at the poles of each magnet, said magnets and pole pieces being located on opposite sides of and oriented obliquely to the path of the plate, a linkage interconnecting the sets of pole pieces, and operating electrical contacts one of which is operatively connected to the pole pieces and the other of which is fixed with respect to the magnets.

9. An inductor switch that is actuated by magnetic cooperation with a relatively movable magnetizable plate extending parallel to the path of relative movement of the switch and plate, said switch comprising a frame extending to each side 01' the plate, a pair of magnets fixedly mounted in the frame, pole pieces pivotally mounted at each pole of the fixedly mounted magnets, linkage interconnecting pole pieces on opposite sides to the magnets, said switch being characterized.

by the orientation of the pole pieces which being directed obliquely to the path of relative movement are in alignment with the magnetic field from the magnets to the marginal area of the plate when in contact operating position.

10. An inductor switch that is actuated by magnetic cooperation with a relatively movable ma netizable plate extending parallel to the path of relative movement of the switch and plate, said switch comprising a frame, a magnet mounted on the frame, pole pieces pivotally mounted at the pole faces of the magnet and extending as continuations of the magnet poles in a direction oblique to said path of relative movement, and electrical switch contacts one of which is operatively connected to the pole pieces and the other of which is fixed with respect to the magnet, said switch being characterized by the oblique orientation of the pole pieces such that in contact closing position the pole pieces are aligned with the magnetic field extending from the pole faces to the marginal area of the plate.

11. In an inductor switch device for energizing control circuits according to the presence of a body within a prescribed zone, in combination, a magnetizable plate extending along the zone, a magnet mounted on the body, pole pieces pivotally mounted at the pole faces of the magnet and extending obliquely toward the plate, cooperating electrical contacts one of which is operatively connected to the pole pieces and the other of which is fixed with respect to the magnet, said pole pieces extending in alignment with the magnetic field and being directed toward the marginal area of the plate as the first approaching edge of the plate approaches juxtaposition to the switch.

12. In an inductor switch device for signaling the presence of a body within a prescribed zone, in combination, a magnetizable plate extending along the zone, a magnet mounted on the body with the poles of the magnet directed obliquely toward the plate, pole pieces pivotally mounted at the pole faces of the magnet and extending along the field of the magnet and cooperating electrical contacts one of which is operatively connected to the po1e pieces and the other of which is fixed with respect to the magnet, said contacts and pole pieces being oriented and ar-- ranged to operate in response to relative movement between switch and plate when the marginal area of the plate is in alignment with the obliquely extending pole pieces.

13. In an inductor switch device for signaling the presence of a body within a prescribed zone, in combination, a magnetizable plate extending along the zone, a magnet mounted on the body with the poles of the magnet directed obliquely toward the plate, pole pieces pivotally mounted at the pole faces of the magnet and extending along the field of the magnet toward the plate, said pivoted pole pieces each having an extended end that is generally parallel to the plane of the plate, and cooperating electrical contacts one of which is operatively connected to the pole pieces and moved to contact with the other by rotation of the pole pieces as they continually point toward the approaching marginal area of the magnetizable plate as that edge approaches the switch.

14. In a magnetic induction switch, in combination, a magnetizable plate mounted on a first member, a magnet mounted on a second member, said magnet providing a magnetic field that is adapted to link with the magnetizable plate and which held extends obliquely to the path of movement of the member to link with the nearer marginal area of the plate when the plate is appreaching toward or receding from the switch, a pivotally mounted armature that is oriented to extend along the oblique position or said magnetic field linking the marginal area of the plate and that moves in response to changes in direc tion of the magnetic field as the plate moves relative to the magnet, and cooperating electrical contacts one of which is operatively connected to the armature to be operated as the armature moves in response to changes in direction of the magnetic field.

15. A magnetic induction switch according to claim 14 in which the magnet is U-shaped and its pole faces are perpendicular to the lines of force of the oblique field and the armature is pivoted at the pole faces of the magnet.

16. A magnetic induction switch according to claim 15 in which the armature has a knife edge opposed to the pole faces of the magnet and a counterweight of suilicient magnitude to secure a condition of neutral equilibrium in the armature and attached electrical contact.

17. A magnetic induction switch according to claim 14 in which the poles of the magnet are 18 separated along a line perpendicular to the path of relative movement and parallel to the cooperating magnetizable plate.

18. A magnetic induction switch according to claim 14 in which a second magnet and armature are positioned relative to the first magnet and armature to receive the magnetizable plate between the magnets and in which a linkage interconnects the armatures to assure simultaneous operation of the armatures.

19. A magnetic induction switch according to claim 18 in which the magnets have like poles opposed whereby the pivoted armatures are repelled from each other in the absence of the magnetizable plate.

JGSEPH H. BORDEN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,639,190 Knutse'n Aug. 16, 1927 1,800,126 Williams Apr. 7, 1931 2,482,529 Williams Sept. 20, 1949 FOREIGN PATENTS Number Country Date 517,572 Great Britain Feb. 2, 1940 

